It is desirable in an oil and/or gas well to provide a well tubing with an unrestricted bore for allowing maximum flow of production fluid therethrough. For this reason, it is conventional to use a tubing retrievable safety valve instead of a wireline retrievable safety valve. That is, a tubing retrievable safety valve is threadably connected into the production tubing string and forms a part thereof and has a bore which is substantially the same size as the bore of the well tubing. On the other hand, a wireline retrievable safety valve is installed on the interior of the well production tubing and consequently has a bore which is considerably smaller than the bore of the well tubing and therefore restricts fluid flow. In the event that the tubing retrievable safety valve fails for some reason it is conventional to lock out the tubing retrievable safety valve and thereafter install a wireline retrievable safety valve in the well tubing as disclosed in U.S. Pat. Nos. 3,696,868 and 3,799,258. However, the newly added wireline retrievable safety valve would undesirably restrict fluid flow through the well tubing.
The present invention is directed to a redundant safety valve system and method of installation which while using both a tubing retrievable safety valve and a wireline retrievable safety valve avoids unduly restricting production through the well tubing.